With the rapid development of transportation, communication and information industry and increasingly serious energy crisis, and with birth and development of electric vehicles and various portable devices, it is urgent to require an alternative energy with high performance. Because a secondary lithium battery has the advantages, such as high energy density, high cycle performance and low self-discharge rate and the like, it becomes an ideal choice for the alternative energy as a chemical power source. At present, it has been widely used in notebook computers, smart phones, electric tools and other consumer electronics, and has made considerable development and progress in fields of electric vehicles, energy storage batteries and the like in recent years,
The application field of the lithium-ion battery continues to expand rapidly, while the safety performance is always a key issue to be concerned and resolved in the lithium-ion battery industry, and becomes an important factor in determining the development prospects of lithium-ion battery. Causes of safety accidents of the lithium-ion battery include a battery internal short circuit and an external abuse. The factors associated with abuse mainly include external environment overheating, external short circuit, overcharge/overdischarge, and nailing, crushing, impact and other mechanical shocks. In accordance with the level of risk, the safety accidents caused by the above potential safety hazards can be divided into battery swelling, breakage of packaging, smoking, firing, and explosion caused by thermal runaway.
Eliminating the potential safety hazards and reducing the level of risk are effective ways to improve the safety performance of the lithium-ion battery. And, increasing lengths of a part of an aluminum foil current collector not provided with a positive active material layer and a part of a copper foil current collector not provided with a negative active material layer of a wound-type cell at an ending part is one technique widely used currently. Although the redundant part of the aluminum foil current collector not provided with the positive active material layer and the redundant part of the copper foil current collector not provided with the negative active material layer of the wound-type cell at the ending part can surround the cell, internal short circuits can be effectively converted to external short circuits in the cases of nailing, crushing, impact, so as to avoid thermal runaway occurring inside the lithium-ion battery caused by too large current, and in turn to reduce serious accidents such as burning and explosions. But at present the biggest obstacle in such a technology is at the expense of a volumetric specific energy of the battery as a precondition.